Integrated circuits (ICs) have been widely used in a variety of applications, such as industrial equipments, measuring equipments, and computer facility. The operation of the ICs generates a great amount of heat and the heat must be timely removed otherwise ICs cannot operate properly if the temperature rises to exceed temperature limitation thereof.
Thus, the IC devices must be combined with a heat dissipation device in order to properly dissipate the heat generated by the ICs and thus maintaining proper working temperature thereof. This is particularly true for a central processing unit (CPU), which is the core of the operation of a computer system, and maintaining proper temperature is even more severe.
With the increase of operation speed of the central processing unit and the ICs, improvement of the performance of the heat dissipation device that removes heat from the central processing unit or ICs is continuously required. This makes the conventional heat dissipation devices, which is comprised of fins and plates, is inefficient for the up-to-date ICs. Fans and heat pipes are commonly combined with fins and plates to enhance heat removal performance of the heat dissipation devices.
As compared to desktop computers, notebook computers or tablet computers often have a very compact size and construction and thus a very limited internal space for arrangement of the heat dissipation devices. This makes it even more difficult to properly remove heat from the notebook computers or tablet computers.
FIGS. 1-3 of the attached drawings show a conventional structure of a heat pipe, wherein FIG. 1 is an overall structure of the conventional heat pipe, FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, and FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 1. The conventional heat pipe, which is generally designated with reference numeral 1 in FIGS. 1-3, comprises a casing having an inner wall 11 and a plurality of internal grooves 12 defined in the inner wall 11 for accommodating a working fluid 13. Each internal groove 12 extends in an axial direction of the heat pipe 1 in a substantially parallel manner. A central channel 14 is formed inside the casing and surrounded by the inner wall 11.
Also referring to FIGS. 4 and 5, which show a perspective view and an exploded view, respectively, illustrating a conventional heat dissipation module, generally designated with reference numeral 2, incorporating the conventional heat pipe 1 discussed with reference to FIGS. 1-3. The heat dissipation module 2 is placed in physical contact with a top face of a heat generating device 3, such as a CPU. The heat dissipation module 2 comprises a heat conduction case 21, a fan 22, a fin assembly 23, and a heat dissipation case 24. The heat pipe 1 is attached to the heat dissipation module 2 and straddles between the heat conduction case 21 and the heat dissipation case 24.
In the heat dissipation module 2, the fan is arranged between the heat conduction case 21 and the fin assembly 23. The fin assembly 23 is received and retained inside the heat dissipation case 24 and forms a plurality of airflow passages (not labeled) for airflows caused by the operation of the fan 22. The airflows caused by the fan 22 facilitate heat removal from the fin assembly 23 to dissipate heat generated by the heat generating device 3.
The heat pipe 1, when mounted to the heat dissipation module 2, can be imaginarily divided into three sections, namely a heat receiving section 15, a heat transfer section 16, and a heat dissipation section 17. The heat receiving section 15 is coupled to and is in physical engagement with the portion of the heat conduction case 21 that is in contact with the heat generating device 3 to receive heat therefrom, and the heat dissipation section 17 is coupled to the fin assembly 23 whereby the heat generated by the heat generating device 3 is transmitted through the heat receiving section 15, the heat transfer section 16, and the heat dissipation section 17 to the fin assembly 23, which, with the aid of the airflows caused by the fan 22, effectively dissipates the heat transmitted to the fin assembly 23 into the surroundings.
During heat dissipation, the internal grooves 12 of the heat pipe 1 extending parallel and axially have a short flow path for the working fluid and thus the working fluid 13 that is accommodated in the internal grooves 12 evaporates by absorbing heat at the heat receiving section 15 and the vapor of the working fluid 13 flows along the central channel 14 from the heat receiving section 15, through the heat transfer section 16, to the heat dissipation section 17 where the heat carried by the vapor is released to the fin assembly 23 and the vapor condensed back into liquid forms that flow along the internal grooves 12 back to the heat receiving section 15.
The heat dissipation module incorporating heat pipe is effective in heat removal for notebook computers or tablet computers that have a very limited internal space. However, the performance of the conventional heat pipe can still be further improved.
For example, the internal grooves 12 and the central channel 14 of the conventional heat pipe are all arranged in a manner that they are substantially parallel and extend in an axial direction of the heat pipe. When the heat pipe is heated by heat energy from for example a CPU, the working fluid inside the heat pipe is heated at the heat receiving section and evaporates into a gaseous form to flow along central channel toward the heat dissipation section, where the vapor condenses into liquid form by releasing heat. By means of pressure difference between the heat receiving section and the heat dissipation section, together with capillary induced by surface tension of the liquid form working fluid, the working fluid flows along the internal grooves back to the heat receiving section to receive heat again. A continuous heat receiving and releasing cycle is thus established.
In the conventional heat pipe, although high flow speed of the working fluid can be obtained in the internal grooves, yet uniform heating and cooling of the working fluid in all the internal grooves is very difficult, and the thermal capacity of the working fluid is not fully exploited and thus overall performance is reduced.
Such a drawback of the conventional heat pipe is due to that the internal grooves are substantially uniformly distributed in a circumferential direction, while only a circumferential portion of the heat pipe at the receiving section is in physical engagement with the heat generating device or the heat conduction case of the heat dissipation module. This means that most of the heat from the heat source is absorbed by the working fluid inside the internal grooves that are located close to the heat source, while the amount of heat absorbed by the working fluid inside the internal grooves that are away from the heat source is relatively low. Thus, the working fluid inside the heat pipe is not heated uniformly, leading to poor exploitation of the thermal capacity of the working fluid.